The present invention relates to the production of stereoscopic pictures of the type employing a lenticular screen.
A well-known technique for producing a stereoscopic picture of a given scene is to photograph the scene a number of times from different vantage points or angles with respect to the elements or objects in the scene. Normally, the successive picture-taking vantage points all have the same vertical elevation and are spaced apart horizontally at equal intervals either along a straight line or the arc of a circle.
It is also known to photograph the scene a number of times from a single vantage point and to translate or rotate the scene relative to the photographic position for each successive picture. The latter technique is entirely analogous to the former one since the relative positions of camera and scene are varied in the identical manner.
There are essentially two methods whereby the photographic images for a stereoscopic picture are caused to be registered on a film or plate behind a lenticular screen: these are the so-called "direct" and the "indirect" methods. In the direct method a lenticular screen is arranged in the camera immediately in front of the photographic negative. After each exposure of the negative (if separate pictures are taken at different relative positions of the camera and scene) or during exposure of the negative (if the relative positions of camera and scene are continuously changed while a single time-exposure is taken), the lenticular screen is moved laterally with respect to the negative or the negative and screen are moved together in the same direction as the camera (if lenticular film is used), so as to maintain successive images of the so-called "key subject matter" of the scene in registry with a selected point on the lenticular screen. After the negative has been fully exposed, it is removed from the camera and developed in the normal way to produce a print or transparency. Finally, another lenticular screen (assuming lenticular film is not employed) is superimposed in proper registry on the print or transparency to complete the stereoscopic picture.
One technique for producing pictures according to the "direct" or in-camera method is fully described, for example, in the U.S. Pat. No. 3,380,360 to Stockbridge, et al.
With the "indirect" method of taking pictures a lenticular screen is not used in the camera and a separate negative is exposed at each different relative position of the camera and scene.
After exposure, the negatives are developed and successively projected and imaged by an enlarger upon photosensitive film which is overlaid with a lenticular screen. The negatives are so projected that the successive narrowed image bands, which are focused on the film by the lenticular screen, lie adjacent to one another on the film. This technique of successive imaging is known in the art as "composing" the stereoscopic picture.
Thereafter the photosensitive film is developed and the same or an identical lenticular screen to that used for composing is properly registered with the composite image to present a stereoscopic picture to the viewer.
Important and useful improvements in the foregoing composing technique, as applied to the indirect photographic method, are described in the copending commonly-owned U.S. patent application Ser. No. 379,388, filed July 16, 1973, by Jerry C. Nims and Allen K. Lo, now U.S. Pat. No. 3,895,867 which copending application is a continuation-in-part of application Ser. No. 171,269 filed Aug. 12, 1971.
In order to obtain photographic negatives, whether by the direct or indirect photographic method, the photographer may adjust one or more of a large number of variables within his immediate control. These variables include such knowns and unknowns as the desired size of the stereoscopic picture to be produced, the resolving power and lenticule width of the lenticular screen, the number and size of two-dimensional picture negatives which are to be taken and included in the stereoscopic picture, the distance between adjacent camera vantage points from which the negatives are taken, the camera focal length, the distance from the camera to the nearest element or object of the scene to be photographed, the distance from the camera to the farthest element or object of the scene to be photographed, and the distance from the camera to an element or object -- the "key subject matter" - in the scene which is to lie in the plane of the picture. Not only is the coordination of these numerous variables an extremely difficult task for a photographer in the field, but it has not previously been known how these variables may be adjusted so that the resulting stereoscopic pictures will be of consistently high quality.